1. Field of the Invention
The invention relates to a galvanically-isolated, low-profile micro-inverter primarily, though not exclusively, intended for use in solar power installations and particularly to an advantageous mechanical arrangement for implementing the micro-inverter.
2. Description of the Prior Art
Currently an increasing worldwide emphasis is being placed on exploiting clean, renewable energy sources rather than fossil fuels. One such source that is receiving considerable attention in the marketplace is solar energy. It is readily abundant, weather permitting, in a wide multitude of locales and across widely differing climates.
In essence, an amount of solar energy is harvested and converted into electrical power which, in turn, is either used to power local loads and/or fed to a power grid for consumption at remote locales from the point at which the energy was harvested. To do so, a matrix of inter-connected photovoltaic elements, called a “solar panel” is aimed at the sun and converts incident solar radiation into a direct current (DC) output. Oftentimes, this DC output is converted through a companion micro-inverter, into appropriate alternating current (AC) line power, to provide an electrical power source for powering local line-powered devices and/or supply the resultant AC power as input to a power grid. The micro-inverter generally employs internal DC-to-DC converter and chopper stages with the DC-to-DC converter being used to change, with relatively little loss, the DC output voltage produced by the solar panel to a level suitable for efficient conversion to the power line AC level.
Oftentimes, a solar power installation utilizes individual assemblies of one or two panels that are mounted to a racking system. The output of the panels in each single assembly is connected to a micro-inverter which, itself, is mounted to the assembly but directly behind the racking system.
Such a conventional approach carries a number of practical constraints. First, to generate a sufficient amount of power for a given application, quite a number of solar panel assemblies may well be needed. Since each assembly has its own micro-inverter, then correspondingly a considerable number of micro-inverters may be needed. To provide requisite economic viability of a solar installation in light conventional utility service pricing, each entire assembly certainly including the micro-inverter must be relatively low cost. Further, limited space exists directly behind a racking system, so that each micro-inverter must fit into a relatively low-profile enclosure, typically not more than 1.25″ (approximately 3.2 cm) thick. Also, as micro-inverters will be exposed to the same harsh environment as a solar panel with a lack of active external cooling systems, each micro-inverter must be completely sealed and passively cooled.
In addition, for safety reasons, each micro-inverter should galvanically isolate its DC power input from its AC output. To achieve galvanic isolation, a transformer would generally be employed within the DC-to-DC converter stage. However, doing so would require a low-profile transformer thin enough to fit within a 1.25″ thick micro-inverter enclosure. Unfortunately, such a transformer is not commonly available, and would thus need to be both designed and manufactured on a custom basis. This, in turn, could potentially and disadvantageously add considerable expense to the cost of the micro-inverter. Consequently, to reduce cost, various manufacturers of conventional micro-inverters, currently available in the commercial marketplace and designed for solar panel use, apparently and unfortunately forego the benefits of providing an isolated AC output by choosing instead to rely on a non-isolated, buck-style DC-to-DC converter design that does not utilize a transformer.
Therefore, a need exists in the art for a low-profile micro-inverter primarily, though not exclusively, suited for use in solar power applications that not only is relatively low cost, completely sealed and passively cooled and fits within available space behind a solar panel racking system in a solar panel assembly, but also and rather advantageously provides galvanic isolation between its DC input and AC output. It is expected that, over time, such a micro-inverter, which overcomes deficiencies inherent in conventional solar power micro-inverter, designs, might likely experience considerable interest and commercial use in solar power installations.